Geoscience Reference
In-Depth Information
Table 8.11
Anisotropy of upper-mantle rocks
Mineralogy
Direction
V
p
V
s
1
V
s
2
V
p
/
V
s
Peridotites
100 pct. ol
1
8.7
5.0
4.85
1.74
1.79
2
8.4
4.95
4.70
1.70
1.79
3
8.2
4.95
4.72
1.66
1.74
70 pct. ol,
1
8.4
4.9
4.77
1.71
1.76
30 pct. opx
2
8.2
4.9
4.70
1.67
1.74
3
8.1
4.9
4.72
1.65
1.72
100 pct. opx
1
7.8
4.75
4.65
1.64
1.68
2
7.75
4.75
4.65
1.63
1.67
3
7.78
4.75
4.65
1.67
1.67
Eclogites
51 pct. ga,
1
8.476
4.70
1.80
23 pct. cpx,
2
8.429
4.65
1.81
24 pct. opx
3
8.375
4.71
1.78
47 pct. ga,
1
8.582
4.91
1.75
45 pct. cpx
2
8.379
4.87
1.72
3
8.30
4.79
1.73
46 pct. ga,
1
8.31
4.77
1.74
37 pct. cpx
2
8.27
4.77
1.73
3
8.11
4.72
1.72
Manghnani
and
Ramananotoandro
(1974),
Christensen
and
Lundquist (1982).
also be enriched in refractory and buoy-
ant products of mantle differentiation such
as olivine and orthopyroxene (
the mantle
perisphere
). The base of this region may be
related to the
Lehmann discontinuity
.
Perisphere
is derived from the prefix
peri
-mean-
ing
all around
,
surrounding, near by
.
Peri
in Persian
folklore is a supernatural being descended from
fallen angels or supernatural fairies and excluded
from paradise until penance is done. The peri-
sphere is mainly buoyant refractory
peridotite
.It
may be enriched in the large-ion lithophile (LIL)
elements, probably as a result of extraction of
these elements from slabs. A shallow enriched
layer
Table 8.12
Measured and estimated
properties of mantle minerals
V
p
V
s
ρ
Mineral
(g/cm
3
)
(km/s)
V
p
/
V
s
Olivine (Fa
.
12
)
3.37
8.31
4.80
1.73
β
-Mg
2
SiO
4
3.63
9.41
5.48
1.72
γ
-Mg
2
SiO
4
3.72
9.53
5.54
1.72
Orthopyroxene
3.31
7.87
4.70
1.67
(Fs
.
12
)
Clinopyroxene
3.32
7.71
4.37
1.76
(Hd
.
12
)
Jadeite
3.32
8.76
5.03
1.74
Garnet
3.68
9.02
5.00
1.80
is
one
alternative
to
a
primordial
deep
Majorite
3.59
9.05
∗
5.06
∗
1.79
∗
layer.
There is evidence that two or three dis-
tinct lithologies contribute to the petrogenesis
of observed magmas. These probably correspond
to recycled components such as oceanic crust,
delaminated lower continental crust and peri-
dotite.
Perovskite
4.15
10.13
∗
5.69
∗
1.78
∗
(Mg.
19
Fe.
21
)O
4.10
8.61
5.01
1.72
Stishovite
4.29
11.92
7.16
1.66
Corundum
3.99
10.86
6.40
1.70
∗
Estimated.
Duffy and Anderson (1988), Weidner (1986).
